ABSTRACT
Micrometer-Sized Particles . . . . . . . . . . . . . . . . . . . . 92
Process for Making Gels . . . . . . . . . . . . . . . . . . . . . 92
Effect of H2O and Hcl Content of the
Starting Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Effect of the Concentration of the Solutions . . . . . . 93
Effect of the Kind of Alkoxides,
Acids, and Alcohols . . . . . . . . . . . . . . . . . . . . . . . . 93
Mechanism of the Formation of Micrometer-Sized
Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
29Si NMR Spectra of the Gels . . . . . . . . . . . . . . . . . 93
Instability of Particles in Organic Liquids . . . . . . . 94
Instability of Particles under Centrifugation . . . . . . 94
Mechanism of the Formation of Round Particles . . 95
Surface Changes in the Ambient Atmosphere . . . . 95
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Formation of silica gels composed of micrometer-sized particles from highly acidic solutions of tetramethox-
ysilane (TMOS) is described. In this method a limited amount of H2O and a large amount of HCl are used in
hydrolyzing TMOS. Detailed conditions and the mechanism of the formation of micrometer-sized particles in
the solutions are discussed. Applications of the gels are also described.
